The present invention relates to the treatment of speiss and, more particularly, to the separation, recovery and purification of arsenic and antimony from the speiss by a roasting operation and a leaching process.
Many ores contain significant amounts of arsenic and antimony in addition to other elements. Some ores, in particular lead ores, contain large amounts of copper and other speiss forming metals and are conventionally processed by roasting and sintering the ore concentrate and then smelting the sinter in a blast furnace. Molten lead bullion from the furnace may then be treated in a variety of ways to separate the lead from the other constitutents of the bullion. U.S. Pat. No. 4,404,026 shows both a conventional drossing purification operation whereby matte and speiss phases are separated from the bullion and an improved method to produce purer matte and speiss phases by using sodium addition to the bullion. The disclosure of this patent is hereby incorporated by reference.
The matte phase is composed primarily of a PbS-Cu.sub.2 S mixture while the speiss phase consists of Cu.sub.3 As, Cu.sub.3 Sb and Fe.sub.2 As, usually intermingled with an additional emulsion of very fine PbS-Cu.sub.2 S matte particles. The matte phase which contains, by weight, mostly copper, about 50%, and lead, about 11%, and small amounts of arsenic, antimony and precious metals, e.g., silver, is typically added to the copper converters in the copper circuit to recover the copper and produce blister copper.
The speiss phase contains, by weight, mostly copper, about 50-60%, lead about 8-12%, and a large percentage of the arsenic, antimony and silver of the lead ore. Normally the speiss is also added to the copper circuit at the copper roaster stage to recover the copper and silver values but the presence of the arsenic and antimony impurities leads to a build-up of these metals in the circuit and to environmental as well as impurity problems in the copper refining process. One practice is to dilute the level of these impurities by stockpiling the speiss and limiting the amount of speiss processed. This practice is uneconomical since the copper and silver are tied up in inventory instead of being produced into finished products.
Accordingly, it is an object of the invention to separate arsenic and antimony from speiss.
It is another object of the invention to treat the recovered arsenic and antimony from the speiss to separate the arsenic from the antimony in a commercially pure form.
It is still another object of the invention to provide a lead ore treatment process whereby the recovery of the copper and silver in the ore is enhanced in the copper circuit by the removal of arsenic and antimony from the speiss.
Additional objects and advantages will be readily apparent as the invention is hereinafter described in detail.